Problem: Kevin starts counting at 40, and he counts by fives. If 40 is the 1st number that Kevin counts. what is the 13th number that he counts?
Explanation: What is the first number that he counts? $40$ What is the second number that he counts? $\begin{align*}&40 + 5 \\ &= 45\end{align*}$ What is the third number that he counts? $\begin{align*}&40 + 5 + 5 \\ &= 40 + (2 \times 5) \\ &= 50\end{align*}$ What is the 13th number that he counts? $\begin{align*}&40 + (12\times5) \\ &= 40 + 60 \\ &= 100\end{align*}$